The present invention relates to an improvement in the design and the method of propelling marine vessels whether they be surface ships or those designed to operate in a submerged configuration. More specifically, the invention described here has the advantages of producing very little drag resistance, of operating at a high degree of efficiency, of being capable higher speeds, and of producing small wakes and a low noise signatures. Additionally, the instant invention is particularly applicable for highspeed marine vessels and especially those that are designed for submerged operation and those employing twin-hull designs. It can also be adapted for marine nozzles for drag reduction.
Most existing designs and the methods employed in the construction of the hulls of marine vessels are based on the use of an immobile watertight hull that is fixedly attached to a solid inner frame. This basic structure is then propelled by an aft propeller that is rotationally driven by an internal drive motor in one direction to force the entire vessel forward or to reverse the direction of propeller rotation which will act to pull the vessel rearward.
As a marine vessel travels through a body of water there is always a relative speed between the outer hull of the vessel and the water that it is in contact with it. This relative speed causes a speed gradient which subsequently causes a resistance that is opposite to the movement of the vessel. The resistance which is commonly known as drag or hydrodynamic drag. According to theory of hydrodynamics, drag resistance is approximately proportional to the square of the velocity. So drag resistance accounts for an important part of the overall resistance when the vessel is traveling at speed exceeding 30 mph.
The use of moving surface to reduce drag has been well established in the prior art with many proffered examples such as that shown by U.S. Pat. No. 532,220 issued to J. Thomas on Jan. 8, 1895 which generally disclosed a mechanism to cover the sides of the ship with revolving belts to reduce friction between the ship and water. At the same time, U.S. Pat. No. 532,221 was issued to J. Thomas on Jan. 8, 1895 in which he additionally patented the driving and support mechanism for the revolving belts that were the subject of the first patent. In both patents the belts were open on the sides which created very complex problems with their sealing which has proven prohibitive. Therefore, the inventions covered by U.S. Pat. No. 532,220 and U.S. Pat. No. 532,221 have found little practical use.
Subsequent to the issuance of the above described patents, U.S. Pat. No. 1,258,428 was issued to J. B. Marling which generally disclosed a marine vessel which employed the use of a rotary bottom in which rows of hollow drums were fixed in tandem in the bottom of the vessel to reduce hydrodynamic drag. The design of this mechanism allow the rotationally attached plurality of drums to freely rotate as the boat moves through a body of water. Subsequent to the publication of this patent, it was discovered that the drums must be very large in diameter and the load speed also be relatively small to obtain the intended benefit of friction reduction. Since this design problem severely limited the usefulness of the invention, it has never made a significant impact on the design or construction of marine vessel hulls.
A method of producing a high speed boat is provided for in U.S. Pat. No. 1,913,605 issued to W. D. on Nov. 5, 1932 in which an endless belt that was attached to the bottom of the boat was used to propel the vessel. The proffered belt was straight in the width dimension and a plurality of air bags were fixed on the wetted side to provide the floating force. One major disadvantage of this design is that at high speed the air bags picked up a lot of water and splashes into the cargo area consuming extra energy and making the vessel less efficient. Additionally, the use of the belt for propulsion purposes is entirely contrary to the intended purpose of lessening the friction between the hull of the vessel and the body of water through which it is passing.
As a similar mechanism is provided for in U.S. Pat. No. 2,377,143 issued to J. V. Golden on Apr. 27, 1942 in which a revolving endless belt was used to form the bottom surface of a marine vessel in an attempt to overcome the drag created as it passed over a body of water. The problem with the design of this example of the prior art is that the belt must be sealed along its entire length along both sides which causes a great deal of friction which consumes a substantial amount of additional energy.
A similar conveyor system is covered by U.S. Pat. No. 3,205,852 issued to B. W. Shepard on Dec. 17, 1964 in which a conveyor forming the bottom of the hull of a marine vessel is used as the propulsion mechanism. The appreciable difference of this invention and the prior art is that it changed the drive and support mechanism of the W. D. Martin invention by allowing the variation of the angle of attack by the bottom of the boat. Again, the problem with this mechanism is that use of the belt for propulsion purposes, irrespective of its angle of attack, is entirely contrary to the intended purpose of lessening the friction between the hull of the vessel and the body of water through which it is passing.
In the continuing line of the review of the prior art, an endless belt system covered in U.S. Pat. No. 3,621,803 issued to R. E. Foster on Sep. 15, 1969 in which a plurality of such belts are provided with the intent of reducing the drag on the vertical sides of the hull of a marine vessel. With this intention, he introduced a plurality of endless belts in tandem to cover a large surface area and provided a workable mechanism to seal the opening on both sides of the belt. The primary problem with this approach to the problem is that the use the plurality of these endless belts is that the areas in front of, in between, and behind these areas can cause turbulence as they pass through the water which in turn create drag which reduces the efficiency of the vessel.
Finally, a method of modifying the dynamic interaction between water and the surface of a vessel is covered in U.K. Pat. No. 2,223,821 issued to Ian Roebuck on Apr. 18, 1990 in which the surface of a marine vessel is covered with a specially designed membrane. The invention operates to reduce drag and noise produced by the hull of a marine vessel passing through a body of water by providing, over a substantial portion of the hull, a flexible surface membrane and means of establishing a transverse displacement wave pattern in that membrane. The problem with this design is that it is very complicated and is therefore limited.
From the foregoing discussion it can be seen that it would be advantageous to provide a method of reducing the hydrodynamic drag that is created between the hull of a marine vessel and the body of water it is passing through as it moves. Additionally, that it would be advantageous to provide such a method that can be implemented over the substantial majority of the surface of the hull that comes into contact with the water in travel.
It is the primary objective of the present invention to provide a method of reducing the hydrodynamic drag that is created between the hull of a marine vessel and the contacting surface of the water it is passing through as it moves along its intended path.
It is an additional objective of the present invention to provide such a method that can be implemented over the substantial majority of the surface of the hull that comes into contact with the water during vessel operation.
It is a further objective of the present invention to provide such a method of producing a marine vessel with a hull design which significantly reduces the hydrodynamic drag on the vessel.
The objectives of the present invention are addressed to reduce the effects of hydrodynamic drag which accounts for an important portion of efficiency robbing resistance to marine vessels. The invention solves the problem of drag resistance for higher-speed marine vessels by providing a mechanism that will reduce or even eliminate the drag along the water-solid interface at the hull of the marine vessel. This mechanism is made up of a revolving elastic shell which is similar to a conveyer belt. However, this similarity ends in the fact that the belt is curled up on itself and sealed along the side edges to form a tubular apparatus which can be inflated with a gas to counter the hydrostatic pressure of the water outside.
This endless tubular belt that is used to form the hull of a marine vessel generally terminates just at the bow of the vessel and out front of the stern. This configuration leaves a hollow tube down the center of the hull which is capped off on either end to form a water-tight hull. Additionally, these caps are fitted with specially designed low friction skirts that interacts with the endless belt to form a water-tight seal and to prevent water from getting into the hull.
An interior frame is employed in the center tube chamber to provide a point of attachment for the engine and a platform for the carrying of cargo or personnel. This interior frame is suspended within the confines of the endless belt hull by the use of a plurality of rollers that are positioned against the inside of the belt in a manner which supports the frame while allowing the belt to rotate freely. The engine thus positioned is used as the propulsion device of the vessel and is generally connected by common means to a revolving propeller which provides the necessary thrust to move the vessel.
This endless elastic belt being so constructed is then free to revolve under the drag force created as the marine vessel travels forward through a body of water. This hydrodynamic drag force causes the belt to remain relatively stationary in relation to the surface of the water regardless of the direction of travel of the marine vessel or its speed in relation to the surface of the body of water. As a result of the linear velocity of the belt being equal to or slightly less than the speed of the vessel, there is little hydrodynamic drag resistence created between the hull of the vessel and the water surrounding it, which allows the vessel to both operate more efficiently and at higher rates of speed.
A drag-free thrust nozzle is also disclosed. This thrust nozzle uses an endless belt unit as described above which is housed within a rigid outer shell. The nozzle is also equipped with a propellor or similar drive means at its center. Thus, a more efficient nozzle than conventional fixed wall nozzles is disclosed.
For a better understanding of the present invention reference should be made to the drawings and the description in which there are illustrated and described preferred embodiments of the present invention.